a good explanation

[Bas]

I guess that your version is faster, although the difference would be
negligible in this small example. The for loop is probably optimized
for speed under the hood (it is written in C), while the 'while' loop
is performed in python, which is much slower.

Much more important than the speed difference is the clarity: your
version is the accepted practice in the python world, so people will
understand it immediately. It also saves two lines of code. And most of
all, it prevents you from making mistakes: your friend, for example,
has forgotten to increase cnt, so he created an infinite loop!

Bas